Urca Tomer, Debnath Anup Kumar, Stefanini Jean, Gurka Roi, Ribak Gal
School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel.
Department of Physics and Engineering, Coastal Carolina University, SC, USA.
Integr Org Biol. 2020 Sep 8;2(1):obaa026. doi: 10.1093/iob/obaa026. eCollection 2020.
The need for long dispersal flights can drive selection for behavioral, physiological, and biomechanical mechanisms to reduce the energy spent flying. However, some energy loss during the transfer of momentum from the wing to the fluid is inevitable, and inherent to the fluid-wing interaction. Here, we analyzed these losses during the forward flight of the mango stem borer (). This relatively large beetle can disperse substantial distances in search of new host trees, and laboratory experiments have demonstrated continuous tethered flights that can last for up to an hour. We flew the beetles tethered in a wind tunnel and used high-speed videography to estimate the aerodynamic power from their flapping kinematics and particle image velocimetry (PIV) to evaluate drag and kinetic energy from their unsteady wakes. To account for tethering effects, we measured the forces applied by the beetles on the tether arm holding them in place. The drag of the flying beetle over the flapping cycle, estimated from the flow fields in the unsteady wake, showed good agreement with direct measurement of mean horizontal force. Both measurements showed that total drag during flight is ∼5-fold higher than the parasite drag on the body. The aerodynamic power estimated from both the motion of the wings, using a quasi-steady blade-element model, and the kinetic energy in the wake, gave mean values of flight-muscle mass-specific power of 87 and 65 W kg muscle, respectively. A comparison of the two values suggests that ∼25% of the energy is lost within the fluid due to turbulence and heat. The muscle mass-specific power found here is low relative to the maximal power output reported for insect flight muscles. This can be attributed to reduce weight support during tethered flight or to operation at submaximal output that may ensure a supply of metabolic substrates to the flight muscles, thus delaying their fatigue during long-distance flights.
长距离扩散飞行的需求会促使对行为、生理和生物力学机制进行选择，以减少飞行过程中消耗的能量。然而，在动量从翅膀传递到流体的过程中，一些能量损失是不可避免的，这是流体与翅膀相互作用所固有的。在这里，我们分析了芒果蛀茎象甲（ ）向前飞行过程中的这些损失。这种相对较大的甲虫能够在寻找新寄主树的过程中扩散相当远的距离，实验室实验已经证明其持续的系留飞行可持续长达一小时。我们让甲虫在风洞中系留飞行，并使用高速摄像技术根据其拍动运动学来估算空气动力功率，同时使用粒子图像测速技术（PIV）从其不稳定尾流中评估阻力和动能。为了考虑系留效应，我们测量了甲虫施加在固定它们的系留臂上的力。根据不稳定尾流中的流场估算出的飞行甲虫在拍动周期内的阻力，与平均水平力的直接测量结果吻合良好。两种测量结果都表明，飞行过程中的总阻力比身体上的寄生阻力高约5倍。使用准稳态叶片元模型从翅膀运动估算出的空气动力功率，以及从尾流中的动能估算出的空气动力功率，分别得出飞行肌肉质量比功率的平均值为87和65 W/kg肌肉。这两个值的比较表明，约25%的能量由于湍流和热量在流体中损失。这里发现的肌肉质量比功率相对于昆虫飞行肌肉报告的最大功率输出较低。这可能归因于系留飞行期间体重支撑的减少，或者归因于在次最大输出下运行，这可能确保向飞行肌肉供应代谢底物，从而在长途飞行中延迟它们的疲劳。
